1. Field of the Invention
The present invention relates to a recording medium used in data storage applications or the like, and also to a tape drive apparatus for driving a tape medium in the form of a tape cassette.
2. Description of the Related Art
It is known in the art to use a tape streamer drive as a drive apparatus for recording and reproducing digital data onto or from a magnetic tape. A typical tape streamer drive has a storage capacity as large as several tens GB to several hundred GB depending on the length of a tape serving as a recording medium disposed in a tape cassette. Because of such a huge storage capacity, tape streamer drives are widely used to keep a backup copy of data stored on a medium such as a hard disk of a computer. Tape streamer drives are also advantageously used to store data with a large data size such as image data.
One known specific tape streamer drive records or reproduces data onto or from an 8-mm VTR tape cassette serving as a recording medium by means of a helical scanning technique using a rotating head.
When data is recorded or reproduced onto or from a tape cassette by the above-described tape streamer drive, preformatting is performed on a magnetic tape of the tape cassette so as to divide the magnetic tape into a plurality of partitions. A data is formed in each partition, and user data is recorded or reproduced into or from the data area.
Referring to FIG. 17, formatting of the magnetic tape and updating of data in a partition performed by the tape streamer drive are briefly described below.
FIG. 17(a) illustrates a part of a magnetic tape in which a partition with a partition number #N and a following partition with a partition number #(N+1) are formed.
A reference/system area is formed at the beginning of each partition #N and #(N+1), as shown in the figure. The reference/system area is used to store information describing the history of use of the magnetic tape and the present partition and also used to store management information required in a recording/reproducing operation. More specifically, the tape streamer drive reads the information described in the reference/system area at the beginning of each partition and controls the operation of recording or reproducing data into or from that partition in accordance with the information described in the reference/system area.
Following the reference/system area, there is provided a data area used to record and reproduce user data. Following the end of the data area, there is placed an EOD (End of Data) code indicating the end of the partition.
In the example shown in FIG. 17(a), an EOD code is placed at the end of each partition with the partition number N or (N+1). This means that the entire recording areas of both partitions are filled with data.
In the magnetic tape shown in FIG. 17(a), data is recorded or reproduced track by track by helical-scanning the magnetic tape using a rotating head. The magnetic tape is formatted such that two adjacent tracks form one frame. Frame numbers are assigned to the respective frames in each partition such that the frame number increases from the beginning of the partition (beginning of the reference/system area) toward the end of the partition (just before the beginning of the next partition). That is, in the case of the partition #N, successive ascending frame numbers are given to respective frames successively formed in an area from a tape position Pst to a tape position Pend.
Maximum frame number information indicating the number of frames formed in the present partition is stored in the reference/system area of this partition.
Note that, for simplicity of illustration, the format shown in FIG. 17(a) is slightly different from the actually used format of the magnetic tape.
When a magnetic tape in the state shown in FIG. 17(a) is given, data in the partition #N may be updated (rewritten), for example, in such a manner that updating of data is started from the beginning of the data area in the partition #N and completed at a data location Prw shown in FIG. 17(b).
At a location following the position at which the writing of data is completed, a new EOD code is placed so as to indicate that the end position of a new valid area of the partition #N is at the position Pnw on the tape.
As can be seen from FIG. 17, the data writing end position indicated by the position Prw on the tape is located before the position at which the data end position was located before updating the data. In this case, the size of the remaining available recording area in the partition #N is given by the sum of the size of a hatched data area and the size of one EOD area.
Because the maximum frame number is described in the reference/system area as described earlier, it is possible to identify the end position of the present partition in units of frames. However, there is no information indicating the end position of the valid data area in the present partition, that is, the tape position Pap in the recording status shown in FIG. 17(b).
Therefore, when data is rewritten from the status shown in FIG. 17(a) into the status shown in FIG. 17(b), it becomes impossible, by using the information stored in the reference/system area, to manage the data area, denoted by means of hatching in FIG. 17(b), located following the end position (Pap) of the valid area.
When an area which cannot be managed is created, a problem can occur as described below.
For example, when a user wants to know the size of an available recording area remaining in a certain partition, it is impossible to calculate the size of the remaining available recording area because the remaining available recording area cannot be managed. This means that the conventional tape streamer drive can have a problem in managing the tape cassette, depending on the recording status because there is no information indicating the end position of the valid area of the present partition (wherein the end position of the valid area can indicate the size of the remaining available recording area).
In view of the above, it is an object of the present invention to provide a more powerful technique of managing a tape cassette employed in a data storage application. More specifically, it is an object of the present invention to provide a technique which makes it possible to manage the remaining available recording area in each partition.
According to an aspect of the present invention, there is provided a recording medium comprising: a tape cassette including a magnetic tape disposed therein; and a memory disposed in the tape cassette, for storing management information used to manage recording or reproducing data onto or from the magnetic tape, wherein the memory includes a memory area for storing: first unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas of each partition when one or more partitions including successive unit recording areas with a predetermined fixed length are formed on the magnetic tape; and second unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas forming a valid area in a partition in which valid data is recorded.
According to another aspect of the present invention, there is provided a tape drive. apparatus comprising tape drive means for recording or reproducing information onto or from a magnetic tape when a tape cassette includes the magnetic tape disposed therein is loaded; and memory drive means for reading or writing management information from or into a memory if the loaded tape cassette includes the memory for storing management information used to manage recording or reproducing data onto or from the magnetic tape, wherein the memory stores first unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas of each partition when one or more partitions including successive unit recording areas with a predetermined fixed length are formed on the magnetic tape; and second unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas forming a valid area in a partition in which valid data is recorded. Preferably, in response to receiving an external command, the memory drive means reads the first unit recording area number information and the second unit recording area number information associated with a particular partition from the memory.
According to the present invention, as described above, the memory disposed in the tape cassette stores management information including first unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas of each partition, and second unit recording area number information indicating the maximum number of successive numbers assigned to unit recording areas forming a valid area in a partition.
Thus, it becomes possible to manage recording areas in the respective partitions other than the valid recording areas using the management information for each unit of recording area.
Furthermore, because information is stored in the MIC, it is possible to quickly obtain information compared with the case in which all information is stored in a management area on the magnetic tape. When information is acquired by reading the management area on the magnetic tape, it is required to move the magnetic tape until it becomes possible to access the management area. In contrast, there is no need to move the magnetic tape in the case where information is read from the MIC.
Furthermore, because the size of a remaining available recording area of a particular partition can be calculated using the first and second unit recording area number information, it is possible to improve the ease of use.
If a frame is employed as the unit recording area, it is possible to calculate the size of a remaining available recording area with an accuracy corresponding to the data length of one frame and thus it is possible to manage the remaining available recording area with the same accuracy.